Photosystem I (PSI) is a crucial pigment-protein complex in thylakoid membranes and drives electron transfer for the fixation of carbon dioxide, which has almost 100% quantum efficiency in converting light energy into chemical energy. To make full use of light energy under different habitats, eukaryotic photosynthetic organisms use multiple types and numbers of light-harvesting complexes (LHCs) to collect light energy and transfer it to PSI reaction centers. Among them, Lhca serves as the light-harvesting antenna of PSI in green algae and land plants, whereas a number of Lhcr, Lhcf, or Lhcq proteins are found in red-lineage algae, including red algae, diatoms, cryptophytes, haptophytes, and dinoflagellates. These varying LHCs absorb light energy and mediate energy balance under different light conditions.